1. Field of the Invention
The present invention relates to a capo device for a stringed musical instrument having series of strings extending along a fretboard with a series of frets, i.e. an instrument such as a guitar, lute, banjo and the like. Such an instrument is played by plucking the strings while using fingers to stop selected strings by holding them pressed down onto the fretboard, the string being “stopped” by the adjacent fret.
2. Prior art.
The present invention is an improvement of the capo devices shown in our Canadian Patent No. 2,244,647, issued Nov. 11, 2000, and our U.S. Pat. No. 6,013,868 issued Jan. 11, 2000.
A capo, sometimes referred to as a “capotasto”, is a device which can be used to hold strings independently of the fingers. Simple capo devices hold all the strings at once, usually against a particular fret, and change the basic key of the instrument. Other devices, referred to as single string capos, are known which can be used to press down and stop only selected strings.
U.S. Pat. No. 5,056,397, which issued Oct. 15, 1991 to Leifheit, was prior art to our aforesaid patents. This shows a kind of capo device for a guitar in which a series of movable capo type elements are provided each with a bore by which the element is slidably mounted on one of the strings and is individually locatable to stop a string at a particular selected location. Each element has an undercut recess in its underside and can be individually held in position by having this recess engage one of the frets, which are made to protrude from the fretboard. The elements of the Leifheit device stop the strings directly, rather than hold the string against an adjacent fret, as is more usual with capo devices.
U.S. Pat. Appln. No. 2002/0112592 to Gillis, published Aug. 22, 2002, shows a guitar with special fret structures which can receive clips capable of holding individual strings at selected stopped positions adjacent the raised portion of the fret structure. Unlike with our previous patent and the Leifheit device, the Gillis clips do not have any bore or aperture by which they are slidably retained on the strings and presumably could be lost.
The invention of our prior patents as aforesaid used movable elements slidably mounted on each of the strings, and magnets were used to hold the capo elements in selected places on the fretboard. The use of magnets is believed to make our elements easier to engage and disengage with the fretboard than those of the Leifheit or Gillis devices. Also, each element of our device stops the strings in the usual way by holding them against adjacent frets, unlike with Leifheit. Our invention also provided a storage area for the elements when they are not in use.
Our aforesaid prior patents covered broadly the idea of using permanent magnets on the fretboard, and/or a permanent magnet or magnets in each movable element. The magnets used in the movable capo elements were single short bar magnets having opposite poles at top and bottom, i.e. remote from and adjacent to the fretboard. While theoretically such movable elements could work with an unmagnetized, ferromagnetic (e.g. steel) fretboard, with magnets available to us at the time of our earlier invention it was preferred to have additional magnets inset in the fretboard to give adequate holding strength. With this arrangement, when the elements were being moved, they “floated” free of the wooden fretboard in between the inset magnets, and this allowed lateral movement to occur accompanied by a tendency for the magnets in the elements to cause these to stick together. For this reason our preference at the time was to use magnets only on the fretboard, and to use plain ferromagnetic steel as the movable elements; this option is shown in FIGS. 6 to 9 of our aforesaid patents.
The use of magnets only on the fretboard is relatively expensive in that many magnets are needed. For example, in the construction of FIGS. 6 to 9 of our patents, showing a six string guitar, twelve magnets are used between each of several adjacent pairs of frets. Using magnets only on the movable elements would result in a less expensive construction using many fewer magnets. Furthermore, when the guitar has steel strings, the presence of magnets in the fretboard can affect the string vibration. The present invention provides a construction in which magnets are used only on the movable capo elements, but in which, unlike in our prior patents, the design of the instrument is such that these magnets do not cause the elements to stick together to any degree that would cause problems. With this construction the fretboard can be simply constructed of ferromagnetic material, and does not need to incorporate magnets.